I've noticed that I'm having a rather hard time trying to retain the things that I learn. I don't really know how to test myself or find ways to use Japanese so that it will become familiar enough. I'm also having a litte bit of trouble using the particles "ni" and "o" and "e" and I still dont understand the difference between wa and ga. Can someone help me.

If you want to test yourself, make a list of questions and a list of answers and keep them separate. Make sure you don't test yourself too soon after studying, when you go to test yourself, look only at the questions, and try to make it random. Take the test, keep in mind you do want to score 100%, but the real goal is to see what you are retaining.